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WG4: Secondary sources of particles and radiation

The research and applications of ultra-intense laser production of secondary sources and material research comprise mainly

  • Fundamental Studies of Laser Matter interaction and secondary source production
  • High yield laser deposition
  • Modification of materials and nanoparticles
  • Synergy of laser irradiation and fast ions irradiation to produce Nanoparticles on large scales

Two main problems arise in the context of inertial confinemnent fusion, which can be syncluded with the above topics.

Laser-Ion Acceleration

A typical PetaWatt-class laser pulse can accelerate ions from a micrometre small source to 10-30% of the speed of light within less than 100 femtoseconds. It is the very accurate definition in space and time, typically referred to as (ultra)small emittance which can enable experiments with sub-picosecond temporal and micrometer spatial resolution.

Such Ion beams accelerated from solid planar targets have exceptional properties, i.e. high brightness and high spectral cut-off, high directionality and laminarity, and short burst duration (∼10-12sec at the source).

More strikingly, ion bunches can be accelerated by the same laser pulses as electron bunches, simply by adjusting focusing and target conditions, see the figure below. This synchronism can be exploited further, ions can be converted into neutrons, relativistic electron pulses are excellent sources of X-UV, X-ray or even Gamma-ray bursts, all with durations of a few femtoseconds or even sub-fs, and all synchronized to within the same time scales. This quality is indeed unique and eventually not even achievable by means other than high power lasers.

Sketch of the concurrent acceleration of electrons and ions to relativistic velocities, through a solid state target foil.

Laser-driven ion beams have a tremendous potential for applications based on the fact that the field structures in which the ions are accelerated have considerably smaller dimensions as compared to conventional accelerators. This may promise more compact and therefore less expensive accelerators in the future. In the last few years, intense research has been conducted on laser-accelerated ion sources and their applications. Large groups are researching in Germany, France, UK, Ireland, Spain, Italy, Czech Rep., Poland, Greece, Portugal.

The relevance of ions generated by laser is increasingly recognized in areas such as medicine, industry, fusion research and development and more basic research.

Several installations exist within the countries of the MP1208 COST consortium which facilitate these studies in secondary sources of particles and radiation. "PetAL" is an ultra high-energy (UHE) multi-kiloJoule Petawatt-class laser being built in France near Bordeaux, and another new generation of laser systems such as the "APOLLON" laser now being built in France will deliver ultra high intensities of up to 1023 W/cm2. These facilities open new and exciting opportunities for laser ion acceleration.

Materials for Laser Fusion

Among the different proposals for Inertial Fusion Energy (IFE) Reactors, the European initiative developed in the past years (HiPER) represents that of Direct Drive (by Shock, Fast Ignition) with no protected chamber. 

 

Interior of the ICF direct drive spherical reactor chamber exposed. Work Group 4 is dealing with challenges around the design of the chamber as well as the production of secondary sources which are used for material stress testing.

A key objective, here, is development of advanced materials for first wall, structural, optics and shielding components.

 

The first wall (FW) solution is based on advanced materials such as nanomaterials, to withstand for long lifetime. We describe the potential synergetic effect of neutron irradiation in ion damage mechanism of FW. The effect of neutron, ions and X-rays in optics is described with conclusions on their relative importance.  In order to maintain the lens temperature constant at any time (start-up, normal operation, different output regime…) we have designed an engineering system based on a cooling fluid. The system has been designed to optimize the most important operation parameters, i.e., uniformity and efficiency, to avoid aberrations and fulfil the final optics demands.

In the Blanket design we work a Dual Coolant Systems with a modular structure in a spherical chamber. He and PbLi are proposed as coolant of First Wall and main system for heat extraction and tritium breeding, respectively. Different proposals have been made to know the role in our systems of Li enrichment, and some conclusions are given; in addition effects of corrosion are considered as an important parameter for final evaluation. The Power Plant cycle has been defined and will be presented.

Concerning the target material, we simulate EOS and phase transitions of Deuterium-Tritium; the mechanical properties under manufacturing conditions with cryogenic temperatures and pressures below 1 Gpa, and shock propagation in Be nano, nanodiamond and foams.

The development of advance materials for first wall, structural, optics and shielding components is a key subject to achieve final goals in IFE Technology.

Recent publications